1. Field of the Invention
The present invention relates to a pluggable optical transceiver with a function of at least one of the optical transmission and the optical reception, in particular, the invention relates to an optical transceiver able to transmit a plurality of optical signals each having a specific wavelength different from others, and to receive a plurality of optical signals each having a specific wavelength different from others.
2. Related Background Art
The United States patent, U.S. Pat. No. 5,943,461B, has disclosed an optical transceiver providing an optical connector coupled with an optical plug attached in a tip of the external fiber. An optical fiber is drawn from the optical connector to couple with an optical subassembly (hereafter denoted as OSA) that installs a semiconductor device, such as semiconductor laser diode (LD) for a transmitter OSA (TOSA) or a semiconductor photodiode (PD) for a recover OSA (ROSA).
The transmission speed of the optical communication has been accelerated and the transmission speed over 10 Gbps, typically 40 Gbps and 100 Gbps, is now available. The semiconductor device in the OSA is quite hard to follow such high speed alone. The intelligent system of the wavelength division multiplexing (WDM) is ordinarily applied. For instance, four signal channels each showing the speed of 10 Gbps and having a specific wavelength different from others are wavelength multiplexed, which equivalently shows the transmission speed of 40 Gbps, and thus multiplexed optical signal is transmitted in the single optical fiber. In the system with the speed of 100 Gbps, four (4) signal channels each having the speed of 25 Gbps are multiplexed or ten (10) signal channels each showing the speed of 10 Gbps are multiplexed to realize the equivalent transmission speed of 100 Gbps. One agreement, CFP-MSA-Draft-rev-1.0, has specified the standard of the 100 Gbps transmission.
An optical transceiver satisfying the WDM standard installs a plurality of TOSAs and ROSAs, an optical multiplexer and an optical demultiplexer. Another type of an optical transceiver for the WDM communication installs an optical unit integrating a plurality of TOSAs with an optical multiplexer and another optical unit integrating a plurality of ROSAs with an optical demultiplexer to eliminate or to decrease the number of inner fibers connecting the optical components. However, such an integrated optical device has a demerit that the whole component is necessary to be replaced even when only one of the TOSAs or only one of the ROSAs becomes failure. In particular, the TOSAs and the ROSAs operable in such high speed region are hard to be available, or often have a restricted margin for the specification; a situation to replace a degraded OSA would be often encountered.
For the optical transceiver installing TOSAs and ROSAs individually, inner fibers coupling each component are scattered. Moreover, the optical fiber has an inherent characteristic to increase the transmission loss by the bending. Conventional optical fiber limits the least bent radius of 15 mm. Even an improved fiber limits the minimum bent radius to be 5 mm. Thus, a surplus length is necessary to be prepared for the inner fibers, which means that lengthy fibers run within the optical transceiver disorderly without adequate wiring of the inner fibers.